From document WO 98/52295 a short-range wireless audio communications system is known, including a miniaturized portable transceiver unit and a base unit transceiver. The miniaturized portable transceiver unit sends and receives information through magnetic induction to the base unit, which may also be portable. Similarly, the base unit sends and receives information through magnetic induction to the portable transceiver. The use of magnetic induction fields limits interference between a plurality of systems operating in close proximity to each other, and it reduces the power requirements. Each of the transducers preferably is a rod antenna such as a ferrite rod within a wire coil. In an embodiment of this known wireless audio communications system multiple transducers arranged in a variety of configurations are provided to generate multiple magnetic fields. In such multiple-transducer embodiments a diversity circuit is used to receive and/or transmit on at least one of the transducers. The generated multiple fields substantially eliminate mutual inductance nulls between the two units which typically occurs at certain positions in a generated magnetic field. The multiple transducers may be arranged in three directions orthogonal to each other. Such an arrangement can comprise ferrite rod transducers and/or loop coil transducers. The three orthogonal transducers can be placed in a corner along the sides of a portable telephone. Alternatively, a loop coil transducer could be placed along the back of the portable telephone, so that it could be made thinner.
EP 0 783 190 A1 relates to a similar RF communication system comprising a transponder unit adapted to communicate with an interrogation unit by transmitting RF signals to and receiving RF signals from the interrogation unit. The transponder unit should be able to effectively receive and transmit RF carrier signals when it is oriented in any of a variety of directions and distances relative to the interrogation unit. In order to achieve that goal the transponder unit is provided with a planar air coil antenna, and two elongated tubular ferrite antennas. The two elongated tubular ferrite antennas are arranged in the same plane as the planar air coil antenna and are perpendicular to each other, so that the maximum sensitivities of the three antennas are arranged in mutually orthogonal directions. Due to the use of three antenna coils the transponder unit can effectively receive RF signals irrespective of the orientation of the transponder unit with respect to the interrogation unit.
The known wireless audio communications system and the known RF communication system, however, have shown the disadvantage that they only consider external interference and nulls of the electromagnetic fields between a transceiver unit (transponder unit) and a base unit transceiver (interrogation unit), but disregard completely interference or nulls of the electromagnetic fields that are caused by the construction of one or both of the devices communicating with each other. However, the inventors have recognized that insufficient reception and transmission of electromagnetic signals is very often caused by unwanted shielding of electromagnetic signals within a communication device or between internal and external areas by components of this device. For instance, components of a communication device like printed circuit boards, displays, batteries shield or at least attenuate electromagnetic fields so that these communication devices show significant directional dependencies in respect of their receiving/transmission capability for electromagnetic signals. This problem increases when the mobile communication device, such as a mobile telephone, is equipped with additional RF communication means like RFID readers/writers, RFID tags or Near Field Communication (NFC) devices. These additional communication means are usually incorporated in packaged integrated circuits which are placed on one main surface of a printed circuit board (PCB). PCBs usually comprise multiple layers, wherein at least one of them is a grounding layer that shields electromagnetic fields. Hence, RF communication between these additional RF communication means and external communication devices is confined to that side of the communication device housing the RF communication means.